/*****************************************************************************
 *  ENTROPY - emerging network to reduce orwellian potency yield
 *
 *  Copyright (C) 2002 Juergen Buchmueller <pullmoll@stop1984.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software Foundation,
 *  Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 *
 *	$Id: peermsg.c,v 1.4 2005/07/12 23:12:29 pullmoll Exp $
 *****************************************************************************/
#include "peermsg.h"
#include "logger.h"

/*****************************************************************************
 *	CRC32
 *****************************************************************************/

static const uint32_t crc_table[256] = {
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
	0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
	0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
	0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
	0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
	0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
	0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
	0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
	0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
	0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
	0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
	0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
	0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
	0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
	0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
	0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
	0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
	0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
	0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
	0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
	0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
	0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
	0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
	0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
	0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
	0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
	0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
	0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
	0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
	0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
	0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
	0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
	0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
	0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
	0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
	0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
	0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
	0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
	0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
	0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
	0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
	0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
	0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
	0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
	0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
	0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
	0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
	0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
};

#define CRC32(crc,val) \
	crc = crc_table[(uint8_t)(crc ^ (val))] ^ (crc >> 8)

/*
 * msg2stream()
 * Serialize the contents of a peer_msg_t structure a 'msg' to
 * a byte stream at 'buff'. Returns the size in bytes in *psize.
 */
int msg2stream(void *buff, peer_msg_t *msg, size_t *psize)
{
	uint8_t *pb = buff;
	size_t i, offs, size;
	uint32_t crc = 0xffffffff;
	uint8_t val;
	FUN("msg2stream");

	size =	1 +			/* sizeof(msg->cmd) */
		1 +			/* sizeof(msg->htl) */
		SHA1SIZE +	/* sizeof(msg->sha1) */
		4 +			/* sizeof(msg->size) */
		msg->size +	/* sizeof(msg->data) */
		4;		/* sizeof(crc) */

	offs = 0;

	/* put the message command */
	val = msg->cmd;
	pb[offs++] = val;
	CRC32(crc, val);

	/* put the message hops to live */
	val = msg->htl;
	pb[offs++] = val;
	CRC32(crc, val);

	/* put the message SHA1 */
	for (i = 0; i < SHA1SIZE; i++) {
		val = msg->sha1.digest[i];
		pb[offs++] = val;
		CRC32(crc, val);
	}

	/* put the message size */
	*(uint32_t*)&pb[offs] = htonl(msg->size);
	val = pb[offs++];
	CRC32(crc, val);
	val = pb[offs++];
	CRC32(crc, val);
	val = pb[offs++];
	CRC32(crc, val);
	val = pb[offs++];
	CRC32(crc, val);

	/* put the message data */
	for (i = 0; i < msg->size; i++) {
		val = msg->data[i];
		pb[offs++] = val;
		CRC32(crc, val);
	}

	/* one's complement of the crc32 */
	crc = ~crc;

	/* store the crc32 of this message */
	*(uint32_t*)&pb[offs] = htonl(crc);
	offs += 4;
	if (size != offs) {
		die(1,"Assertion: size != offs in %s:%d\n",
			__FILE__, __LINE__);
	}

	if (NULL != psize)
		*psize = size;

	return 0;
}

/*
 *	stream2msg()
 *	Unserialize the byte stream from buff and fill a peer_msg_t
 *	structure at 'msg' with the results. Return zero if successful.
 *	If 'csum' is non zero, verify the message validity by comparing
 *	the transmitted and calculated crc32 values for the contents.
 */
int stream2msg(peer_msg_t *msg, void *buff, size_t size)
{
	uint8_t *pb = buff;
	size_t i, offs = 0;
	uint32_t crc = 0xffffffff;
	uint32_t got;
	uint8_t val;
	FUN("stream2msg");

	memset(msg, 0, sizeof(peer_msg_t));
	memset(msg->data, 0, CHUNKSIZE);

	if (size < 1) {
		LOG(L_ERROR,("bogus msg: CMD\n"));
		errno = EINVAL;
		return -1;
	}
	val = pb[offs++];
	msg->cmd = val;
	CRC32(crc, val);
	size--;

	if (size < 1) {
		LOG(L_ERROR,("bogus msg: HTL\n"));
		errno = EINVAL;
		return -1;
	}
	val = pb[offs++];
	msg->htl = val;
	CRC32(crc, val);
	size--;

	if (size < SHA1SIZE) {
		LOG(L_ERROR,("bogus msg: SHA1\n"));
		errno = EINVAL;
		return -1;
	}
	for (i = 0; i < SHA1SIZE; i++) {
		val = pb[offs++];
		msg->sha1.digest[i] = val;
		CRC32(crc, val);
	}
	size -= SHA1SIZE;

	if (size < 4) {
		LOG(L_ERROR,("bogus msg: SIZE\n"));
		errno = EINVAL;
		return -1;
	}
	msg->size = ntohl(*(uint32_t*)&pb[offs]);
	val = pb[offs++];
	CRC32(crc, val);
	val = pb[offs++];
	CRC32(crc, val);
	val = pb[offs++];
	CRC32(crc, val);
	val = pb[offs++];
	CRC32(crc, val);
	size -= 4;

	if (size < msg->size) {
		LOG(L_ERROR,("bogus msg: DATA size have:%04x expect:%04x\n",
			(unsigned)size, (unsigned)msg->size));
		errno = EINVAL;
		return -1;
	}

	if (msg->size > CHUNKSIZE) {
		LOG(L_ERROR,("bogus msg: DATA size expect:%04x > CHUNKSIZE:%04x\n",
			(unsigned)msg->size, (unsigned)CHUNKSIZE));
		msg->size = CHUNKSIZE;
		errno = EINVAL;
		return -1;
	}

	for (i = 0; i < msg->size; i++) {
		val = pb[offs++];
		msg->data[i] = val;
		CRC32(crc, val);
	}
	size -= msg->size;

	/* one's complement of the crc32 */
	crc = ~crc;

	/* this message should have a crc32 attached */
	if (size < 4) {
		LOG(L_ERROR,("bogus msg: CRC32 size have:%04x expect:%04x\n",
			(unsigned)size, (unsigned)4));
		errno = EINVAL;
		return -1;
	}
	got = ntohl(*(uint32_t*)&pb[offs]);
	offs += 4;
	size -= 4;

	if (crc != got) {
		LOG(L_ERROR,("bogus msg: crc mismatch got:%08x want:%08x\n",
			got, crc));
		errno = EINVAL;
		return -1;
	}

	if (size > 0) {
		LOG(L_ERROR,("bogus msg: %#x trailing bytes after DATA\n",
			(unsigned)size));
		/* just ignore crap for now ... */
	}

	return 0;
}

